The invention presented herein relates to the composition of zirconium (Zr) alloy having a superior corrosion resistance and high strength. In particular, this invention relates to the alloys with superior corrosion resistance and high strength for fuel claddings, spacer grids, and core structural components in light water reactor (LWR) and heavy water reactor (HWR).
Zirconium alloys, in particular Zircaloy-2 and Zircaloy-4, have been widely used as fuel rod cladding and structural elements of nuclear reactor core.
The development of zirconium alloys is illustrated as follows: Zircaloy-1 (Sn: 2.5 wt. %, Zr: the balance); Zircaloy-2 (Sn: 1.20-1.70 wt. %, Fe: 0.07-0.20 wt. %, Cr: 0.05-1.15 wt. %, Ni: 0.03-0.08 wt. %, O: 900-1500 ppm, Zr: the balance; wherein, Fe+Cr+Ni: 0.16-1.70 wt. %); Zircaloy-3A (Sn: 2.5 wt. %, Fe: 0.25 wt. %, Zr: the balance); Zircaloy-3B (Sn: 0.5 wt. %, Fe: 0.4 wt. %, Zr: the balance); Zircaloy-3C (Sn: 0.5 wt. %, Fe: 0.2 wt. %, Ni: 0.2 wt. %, Zr: the balance); Zircaloy-4 (Sn: 1.20-1.70 wt. %, Fe: 0.18-0.24 wt. %, Cr: 0.07-0.13 wt. %, O: 900-1500 ppm, Ni: &lt;0.07 wt. %, Zr: the balance, wherein Fe+Cr: 0.28-0.24 wt. %); and so forth. The above alloys, except for Zircaloy-2 and Zircaloy-4, have not been commercialized due to poor mechanical strength and corrosion resistance in the reactor.
As the operating conditions of nuclear power plants tend to be at high burnup, increased operating temperature, and high pH, Zircaloys could not be utilized as fuel rod cladding. Recently, the extensive and successful research and development have been focused on increasing the corrosion resistance of zirconium alloys.
U.S. Pat. No. 5,254,308 discloses the alloy in which niobium and iron were added to maintain mechanical properties. This alloy comprises tin in the range of 0.45 to 0.75 wt. % (typically 0.6 wt. %); iron in the range of 0.4 to 0.53 wt. % (typically 0.45 wt. %); chromium in the range of 0.2 to 0.3 wt. % (typically 0.25 wt. %); niobium in the range of 0.3 to 0.5 wt. % (typically 0.45 wt. %); nickel in the range of 0.012 to 0.03 wt. %(typically 0.02 wt. %) silicon in the range of 50 to 200 ppm (typically 100 ppm); oxygen in the range of 1000 to 2000 ppm (typically 1600 ppm); and the balance being zirconium, wherein the ratio of iron to chromium (Fe/Cr) was 1.5. The amount of niobium was relatively fixed to that of iron which has effects on the hydrogen uptake. Also, the amount of nickel, silicon, carbon, and oxygen were fixed to maintain the superior corrosion resistance and high strength.
U.S. Pat. No. 5,278,882 also describes the zirconium alloy without niobium which comprises tin in the range of 0.4 to 1.0 wt. % (typically 0.5 wt. %); iron in the range of 0.3 to 0.6 wt. % (typically 0.46 wt. %); chromium in the range of 0.2 to 0.4 wt. % (typically 0.23 wt. %); nickel in the range of 0.012 to 0.03 wt. % (typically 0.02 wt. %); silicon in the range of 50 to 200 ppm (typically 100 ppm); oxygen in the range of 1200 to 2500 ppm (typically 1800 ppm); and the balance being zirconium.
U.S. Pat. No. 5,334,345 discloses the zirconium alloy, which improves corrosion and hydrogen uptake resistance, as follows:
tin, in the range of 1.0 to 2.0 wt. %; PA1 iron, in the range of 0.07 to 0.70 wt. %; PA1 chromium, in the range of 0.05 to 0.15 wt. %; PA1 nickel, in the range of 0.16 to 0.40 wt. %; PA1 niobium, in the range of 0.015 to 0.30 wt. % (typically in the range of 0.015 to 0.20 wt. %); PA1 silicon, in the range of 0.002 to 0.05 wt. % (typically in the range of 0.015 to 0.05 wt. %); PA1 oxygen, in the range of 900 to 1600 ppm; and PA1 zirconium, the balance. PA1 iron, in a range of 0.1 to 0.35 wt. %; PA1 vanadium, in a range of 0.07 to 0.4 wt. %; PA1 oxygen, in a range of 0.05 to 0.3 wt. %; PA1 silicon, less than 0.25 wt. %; PA1 niobium, less than 0.25 wt. %; and PA1 zirconium, the balance. PA1 tin, in a range of 0.2 to 0.9 wt. %; PA1 iron, in a range of 0.18 to 0.6 wt. %; PA1 chromium, in a range of 0.07 to 0.4 wt. %; PA1 niobium, in a range of 0.05 to 0.5 wt. %; PA1 tantalum, in a range of 0.01 to 0.2 wt. %; PA1 vanadium, in a range of 0.05 to 1 wt. %; PA1 molybdenum, in a range of 0.05 to 1 wt. %; and the balance being zirconium. PA1 tin, in a range of 0.2 to 1.15 wt. %; PA1 iron, in a range of 0.19 to 0.6 wt. % (typically 0.19 to 0.24 wt. %); PA1 chromium, in a range of 0.07 to 0.4 wt. % (typically 0.07 to 0.13 wt. %); PA1 tantalum, in a range of 0.01 to 0.2 wt. %; PA1 niobium, in a range of 0.05 to 0.5 wt. %; PA1 nitrogen, less than 60 ppm; and PA1 the balance being zirconium. PA1 niobium, in a range of 0.5 to 1.5 wt. %; PA1 tin, in a range of 0.9 to 1.5 wt. %; PA1 iron, in a range of 0.3 to 0.6 wt. %; PA1 chromium, in a range of 0.005 to 0.2 wt. %; PA1 carbon, in a range of 0.005 to 0.04 wt. %; PA1 oxygen, in a range of 0.05 to 0.15 wt. %; PA1 silicon, in a range of 0.005 to 0.15 wt. %; and PA1 the balance being of zirconium. PA1 tin, in a range of 0.2 to 1.15 wt. %; PA1 iron, in a range of 0.19 to 0.6 wt. %; PA1 chromium, in a range of 0.07 to 0.4 wt. %; PA1 the balance being of zirconium and incidental impurities.
U.S. Pat. No. 5,366,690 describes the another zirconium alloy in which the amounts of tin, nitrogen and niobium were each controlled, containing tin in a range of 0 to 1.50 wt. % (typically 0.6 wt. %); iron in a range of 0 to 0.24 wt. % (typically 0.12 wt. %); chromium in a range of 0 to 0.15 wt. % (typically 0.10 wt. %); nitrogen in a range of 0 to 2300 ppm; silicon in a range of 0 to 100 ppm (typically 100 ppm); oxygen in a range of 0 to 1200 ppm (typically 1200 ppm); and niobium in a range of 0 to 0.5 wt. % (typically 0.45 wt. %).
U.S. Pat. Nos. 4,863,685; 4,986,975; 5,024,809; and 5,026,516 relate to the zirconium alloy with tin (0.5-2.0 wt. %), other alloying elements (0.5-1.0 wt. %), and oxygen (0.09-0.16 wt. %). In the alloy according to the U.S. Pat. No. 4,863,685, the other alloying elements are molybdenum, tellurium, the mixture thereof, Nb-Te, or Nb-Mo. The amounts of copper, nickel, and iron were limited to the range of 0.24 to 0.40 wt. %, and copper was added more than 0.05 wt. %. In U.S. Pat. Nos. 5,024,809 and 5,026,516, alloying elements are added in the range of 0.5 to 1.0 wt. % which is the same as that in U.S. Pat. No. 4,863,685. Bismuth(Bi) or (Bi+Sn) is added to this alloy, and the other alloying elements are molybdenum, niobium, and tellurium.
U.S. Pat. No. 4,938,920 discloses the improved Zircaloy-4 with better corrosion resistance in which tin was reduced to the range of 0 to 0.8 wt. %, and vanadium in a range of 0 to 0.3 wt. % and niobium in a range of 0 to 1 wt. % was added. This alloy includes iron in a range of 0.2 to 0.8 wt. %, chromium in a range of 0 to 0.4 wt. %, and oxygen in a range of 1000 to 1600 ppm. The amount of (Fe+Cr+V) was also limited to a range of 0.25 to 1.0 wt. %. When this alloy was tested in autoclave at 400.degree. C. to measure the corrosion resistance, the weight gain of the alloy with a composition of 0.8Sn-0.22Fe-0.11Cr-0.14O; 0.4Nb-0.67Fe-0.33Cr-0.15O; 0.75Fe-0.25V-0.1O; and 0.25Sn-0.2Fe-0.15V-0.1O decreased down to about 60% weight gain of compared to Zircaloy-4, and the tensile strength of these alloys was the same as that of Zircaloy-4.
U.S. Pat. No. 4,981,527 discloses an advanced zirconium alloy with high uniform and nodular corrosion resistance, which comprises an alloy composition as follows:
The amounts of (Fe+V) are fixed at less than 0.75 wt. % to improve the workability in the process of cold working. The amounts of niobium and tin were limited in accordance with corrosion tests, and oxygen was added to improve hardness and creep resistance. This alloy has high uniform and nodular corrosion resistance in the same metallurgical conditions.
U.S. Pat. No.4,963,323 describes the improved Zircaloy-4 in which the composition is adjusted for use in fuel rod cladding with high corrosion resistance. In this alloy, the amount of tin was decreased, niobium was added to compensate for the decreased tin, and nitrogen was limited to less than 60 ppm. Thus, the improved Zircaloy-4 according to U.S. Pat. No. 4,963,323 comprised tin in a range of 0.2 to 1.15 wt. %, iron in a range of 0.19 to 0.6 wt. % (typically 0.19 to 0.24 wt. %), chromium in a range of 0.07 to 0.4 wt. % (typically 0.07 to 0.13 wt. %), niobium in a range of 0.05 to 0.5 wt. %, and nitrogen up to 60 ppm.
U.S. Pat. No. 5,017,336 discloses the improved Zircaloy-4 which was adjusted by adding with niobium, tantalum, vanadium, and molybdenum, and the alloy composition is as follows:
U.S. Pat. No. 5,196,163 discloses the improved zirconium alloy containing tantalum and niobium as well as the usual composition which are tin, iron and chromium. The alloy composition is as follows:
U.S. Pat. No. 5,560,799 discloses the zirconium alloy, which comprises the following alloy composition.
In this patent, the distance between the precipitates, Zr(Nb, Fe)2, Zr(Fe, Cr, Nb), and (Zr, Nb)3Fe, was limited to the range of 0.20 to 0.40 .mu.m, and the volume fraction of the precipitate containing iron was limited to 60% in precipitates.
U.S. Pat. No. 4,992,240 discloses a zirconium alloy containing the elements tin, iron, chromium and niobium, comprising tin in a range of 0.4 to 0.2 wt. %, iron in a range of 0.2 to 0.4 wt, chromium in a range of 0.1 to 0.6 wt, niobium in a range of 0 to 0.5 wt. % and the balance zirconium.
Also, U.S. Pat. No. 4,963,323 discloses a corrosion resistant zirconium alloy for uses as a reactor fuel cladding material consisting essentially:
CA 2,082,691 describes the zirconium alloy maintaining ductility to that of sponge zirconium and high corrosion resistance by adding bismuth in a range of 0.1 to 0.5 wt. % and niobium in a range of 0.1 to 0.5 wt. % (typically 0.1 to 0.3 wt. %).
The zirconium alloys are suitable for material used in fuel rod cladding because of the small capture cross section of thermal neutron and relatively good corrosion resistance at high temperature. For the present fuel rod cladding, Zircaloys with tin, iron, chromium, and nickel are being widely used for the fuel rod cladding in nuclear power plant.
However, considering the circumstances of the extended and high burn-up fuel, the use of Zircaloys as material for fuel rod cladding becomes limited due to enhanced corrosion and irradiation creep. Therefore, the development of an advanced zirconium alloy with high strength and corrosion resistance has been required.
We, the inventors of this invention, successfully developed a zirconium alloy with higher strength and superior corrosion resistance than the former existing Zircaloys through making changes in the kinds and amounts of alloying elements.